Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

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FXUS63 KLOT 230505
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1105 PM CST Thu Jan 22 2026

.KEY MESSAGES...

- Dangerously cold conditions are expected through early
  Saturday morning, with coldest conditions expected this
  morning.

- Fluffy accumulating snow paired with cold temperatures may
  cause hazardous to locally dangerous travel conditions late
  Saturday into Sunday.

&&

.UPDATE...
Issued at 828 PM CST Thu Jan 22 2026

The forecast is on track this evening.

Recent radar imagery from KLOT shows the leading edge of the
true arctic air now racing across northern Illinois at press
time along the periphery of a building high pressure system in
the northern Plains. Northwesterly winds will increase in
magnitude right behind the front and facilitate aggressive cold
air advection of bitterly cold temperatures from the Upper
Mississippi River Valley into the Lower Great Lakes. The
inherited forecast appears to be right on track with temperature
trends thus far, and will result in low temperatures ranging
from minus 15 near the Wisconsin state line to minus 5 near the
US-24 corridor just after daybreak Friday. When combined with
the wind, it`ll feel closer to minus 35 near the Wisconsin
border to minus 25 near US-24. The Extreme Cold Warning and Cold
Weather Advisories set to go in effect overnight are hence in
good shape.

(Note that the Extreme Cold Warning will convert to a Cold
Weather Advisory at noon tomorrow as wind chills "warm" above
minus 30. We try to confine warning-level products to the time
frame when warning-level impacts will occur. It will still be
uncomfortably cold all the way through Saturday morning, after
which the Cold Weather Advisories across our entire area are
currently set to expire).

Have also been monitoring snow showers organized in horizontal
convective rolls along the Minnesota/Iowa/Wisconsin tri-border
region, which will be poised to drop southward into our area
overnight. The inherited forecast calling for flurries seems
appropriate for this activity, though definitely can`t rule out
a streak or two of a dusting of snow where activity is most
pronounced through daybreak.

The only thing change in our gridded database this evening was
to lower dew points tomorrow and tomorrow night by 5 to 10
degrees to fall in the minus 30 to minus 40 range, in line with
upstream observations across central Minnesota and recent
HRRR/RAP guidance. Otherwise, felt everything else was in great
shape.

Updated products will be sent soon.

Borchardt

&&

.DISCUSSION...
Issued at 249 PM CST Thu Jan 22 2026

Through Friday night...

An arctic cold front will move across the area this evening
ushering in a bitterly cold air mass in its wake. Strong cold
air advection will continue through the night and into Friday,
likely resulting in low temperatures occurring after sunrise
Friday morning. The strong cold air advection will keep boundary
layer well mixed, and when combined with the tight pressure
gradient will result in strong and gusty northwest winds
tonight into Friday morning. The strong winds combined with
subzero air temps will result in dangerously cold wind chills.
The coldest wind chills are expected Friday morning, ranging
from 20 to 30 below over southeastern CWA to colder than 30
below at times northwestern CWA. No changes made to the Extreme
Cold Warning and Cold Weather Advisory through Friday morning.

Not expecting much in the way of a temperature recovery during
the daytime hours Friday as cold air advection continues through
the afternoon. Did nudge high temps upward just a hair Friday,
mainly across Chicago and areas south of I-88 where there is
little or no snow cover. These areas will likely be able climb
just barely above zero, with temps across far northern IL
probably remaining slightly below zero. Winds will gradually
diminish through the day, so wind chills should "warm" above -30
everywhere midday, but likely to remain in the 15 to 25 below
zero range through Friday evening.

Increasing cloudiness Friday night will probably limit temps
from completely crashing, though another night of subzero lows
are expected. Diminishing winds may allow wind chills to creep
above advisory criteria by late Friday night. Did opt to extend
the cold weather advisory through 9 AM Saturday to err on the
side of caution, since it would only take winds a few mph
stronger to result in wind chills at or below advisory criteria.

Finally, satellite imagery shows an extensive field of
horizontal convective rolls across MN, northern IA and WI. While
these clouds are shallow, cloud temps are cold enough for ice
nuclei to be present and it is common for arctic dust type
flurries to fall from these clouds. Have maintained flurries in
the grids through tonight, but wouldn`t be surprising if the
flurry chances need to be carried into the daytime hours Friday.
Can`t rule out some lake effect snow (LES) showers clipping far
northeast Porter County, but with mean flow 310-330, expect the
brunt of the LES to remain east of Porter County. Winds will
veer more northerly Friday night, but also weaken considerably
so while LES will shift westward, it may also tend to remain
mostly over the lake as land breeze develops and possibly
results in lake induced meso-low forming.

- Izzi

Saturday and Sunday...

Forecast attention this weekend focuses on the major winter
storm expected to have significant impacts across a good chunk
of the southern and eastern CONUS. Locally, our area is expected
to remain along the northern periphery of this large and
expansive storm system, which naturally adds question marks with
regards to how far northwest impactful wintery precipitation
will fall. This is especially the case considering that a sharp
north- northwestern cutoff in precipitation could occur over, or
near parts of northwestern IL. Nevertheless, forecast
confidence continues to increase in accumulating snowfall
falling across much of central into northeastern IL and
northwestern IN, most notably during the Saturday night and on
Sunday timeframe.

A robust baroclinic zone will settle south across the southern
states Friday into the weekend along the southern periphery of
the Arctic airmass settling into the area tonight. Friday into
Saturday, upstream height falls resulting form the strengthening
aggregate troughing across the Rockies will induce a
strengthening lower-level southerly mass response from the Gulf
northward across this baroclinic boundary. This will in turn
foster the development of an expansive wintry precipitation
shield from the central and southern Plains late Friday into
Friday night eastward across much of the southern half of the
country Saturday into Sunday.

While a majority of the heavy precipitation with this system is
expected to fall south of our area, as mentioned, chances
continue to increase that much of our local area will experience
some accumulating snowfall late Saturday through Sunday. The
snow may come in two separate waves, with the first potentially
coming Saturday afternoon into the evening, and a second coming
Saturday night and on Sunday. Interestingly, with the Arctic
airmass remaining in place across our area, the thermodyamics
profile in which this snow will be generated within will feature
a very deep Dendritic Growth Zone (DGZ), likely in excess of
10,000 ft. This will in turn foster a higher than average
liquid-to- snow ratio than is typical for our area, with 20-25+
to 1 ratios certainly in play. Accordingly, even a tenth to two
tenths of an inch of QPF that falls could result in a few inches
of dry fluffy accumulation.

While confidence does continue to increase in at least parts of
our local area experiencing some accumulating snowfall Saturday
afternoon into Sunday, uncertainty remains with the specifics.
For example, as noted above, one of the main question marks that
remains is how far northwest into our area accumulating snow
will extend. This as the precipitation looks to fight with drier
air trying to advect into the region from the Arctic high to
our northwest. The other question resides around the extent of
lake enhanced snowfall along the south-southwesterly periphery
of Lake Michigan Saturday night into Sunday. Low-level
thermodynamic conditions do look favorable for this, and there
is concern that this could result in higher snow amounts along
and near the lakeshore into Sunday. Stay tuned for forecast
updates!

One final note: Surface temperatures are expected to be in the
single digits to the teens during the snowfall. Temperatures
this cold will support snow covered roads, as traditional salt
treatments will be less effective then when temperatures are in
the 20s. For this reason, regardless of how much snow falls in a
given area, expect adverse travel impacts in and near the
region late Saturday into Sunday.

KJB

Sunday night through Thursday...

Cooler than average weather conditions are expected to persist
through next week.

Northerly low-level flow is expected to linger Sunday night
into Monday morning, before gradually backing northwest ahead of
a building surface high pressure ridge. This will likely
maintain a threat of accumulating lake-effect snow showers into
northwest IN during this period, and potentially across far
northeast IL (at least Sunday evening) as GFS/GEM guidance
depicts slightly more north-northeasterly flow for a time.
Accumulation potential appears greater in northwest IN however,
with a longer period of favorable fetch and inversion heights
which are progged to gradually rise Monday night beneath the
mid-level trough axis and cold pool (temps approaching -22C at
850 mb). High pressure developing surface and aloft during the
day Monday should eventually limit/end lake-effect for northwest
IN, as subsidence gradually lowers inversion heights and low-
level flow backs westerly.

Otherwise, the main theme through the extended forecast period
will continue to be colder than average weather conditions
across the area through much of next week. There may be some
brief "moderation" in temps to around 20 degrees or so Tuesday
in advance of another mid-level short wave, though a renewed
push of colder air behind this system looks to reinforce arctic
air across the region by mid- week. Aside from Tuesday, blended
NBM guidance indicates daytime temps in the single digits to
lower teens and nighttime lows in the single digits either side
of zero are, with coldest wind chills approaching -15F to -20F
at times. While low-amplitude clipper systems can`t be ruled out
in this persistent northwest flow pattern, there is currently
no signal in ensemble guidance for significant precipitation
beyond the potential Sunday night/Monday morning lake-effect.

Ratzer

&&

.AVIATION /06Z TAFS THROUGH 12Z SATURDAY/...
Issued at 1105 PM CST Thu Jan 22 2026

Expect WNW winds to frequently gust around 25 knots with some
sporadic gusts to 30 knots through around daybreak. Shallow,
narrow ribbons of MVFR stratus possibly containing flurries
should spread southeast across northern Illinois for a few hours
early this morning before dissipating around or after
sunrise/13Z.

VFR conditions with thickening upper-level clouds are expected
today through tonight. WNW/NW winds gusting to around 20 knots
today will veer NNE under 10 knots early in the evening.

Kluber

&&

.HYDROLOGY...
Issued at 828 PM CST Thu Jan 23 2026

Area hydrographs and ice spotter reports confirm that ice
continues to develop, thicken, and spread across areal rivers.
Localized ice jams are already present along the Rock, Des
Plaines, and Fox Rivers. Bitterly cold temperatures tonight
through the weekend will cause ice to continue expanding and
thickening, increasing the threat for ice jams and localized
flooding. At least some moderation in temperatures by the
middle of next week may cause ice to begin shifting, before
another period of bitterly cold temperatures arrives by next
weekend.

- NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Extreme Cold Warning from 3 AM to noon CST Friday for ILZ003-
     ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
     ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ103-ILZ104-ILZ105-
     ILZ106-ILZ107-ILZ108.

     Cold Weather Advisory from noon Friday to 9 AM CST Saturday
     for ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
     ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ103-
     ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.

     Cold Weather Advisory from 3 AM Friday to 9 AM CST Saturday
     for ILZ033-ILZ039.

IN...Cold Weather Advisory from 3 AM CST /4 AM EST/ Friday to 9 AM
     CST /10 AM EST/ Saturday for INZ001-INZ002-INZ010-INZ011-
     INZ019.

LM...Gale Warning until 3 AM CST Friday for Winthrop Harbor IL to
     Gary IN.

     Small Craft Advisory from 3 AM to 3 PM CST Friday for Winthrop
     Harbor IL to Gary IN.

     Gale Warning until 9 AM CST Friday for Gary to Burns Harbor IN-
     Burns Harbor to Michigan City IN.

     Heavy Freezing Spray Warning until 3 PM CST Friday for Gary to
     Burns Harbor IN-Burns Harbor to Michigan City IN.

     Small Craft Advisory from 9 AM Friday to 3 AM CST Saturday for
     Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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